The present disclosure relates to a lead frame, as can be used in particular for the connection of a controlling means usable in a vehicle transmission, and to a method for the production of a lead frame.
Lead frames are used, for example, in motor vehicle manufacturing in order to make electrical contact with control devices. For example, control modules which are installed in an oil-filled transmission interior space are used in motor vehicle automatic transmissions for controlling clutch and gear shifting operations. Insert-molded lead frames are used here for electric line routing.
Lead frames are preferably flat elements on which electronic components can also be mounted. Electrically conductive sections in the form of singular conductor tracks are present on the lead frames, in particular on a core element which is arranged centrally and is surrounded by an electrically insulating casing. The core element is generally produced here from plastic or metal, wherein, in the case of a design from plastic, the conductor tracks are mounted as conductive layers on a carrier substrate.
DE 10 2009 046 467 A1 describes a lead frame with a special surface contour, and a control device with such a lead frame. A conventional method for producing a lead frame is also described.
Summarized in brief, in a first production step, core elements of the lead frames are formed by means of punching methods. The individual core elements are mechanically connected to one another here at a number of points, and therefore it is not necessary for each individual core element to be inserted into a corresponding die during a subsequent insert-molding operation.
The core elements are subsequently insert-molded with a plastic in order to form a casing around the core elements and in order thereby firstly to ensure a necessary electrical insulation to the outside and secondly to achieve mechanical stabilization.
In a second production step, a partial pre-insert molding takes place in the form of a first partial insert-molding of the core elements of the lead frame, in which, however, partial regions, for example the connecting points which hold the individual core elements together, are generally not insert molded. Said partial regions can form opening regions which generally have dimensions of 1 to 2 mm.
In a third production step, the core elements are separated from one another. The connecting points between the core elements are punched out or separated in some other manner here. This gives rise to a multiplicity of individual core elements or conductor tracks which are generally not connected electrically to one another. The previously provided pre-insert-molding generally surrounds a plurality of core elements here and holds said core elements together and in the required geometrical position thereof.
In a final fourth production step, a main insert molding takes place in the form of a second partial insert-molding of the individual pre-insert-molded core elements. In this case, in particular those regions of the lead frame which are not covered by the pre-insert-molding are insert-molded, but also the pre-insert-molded regions can be partially insert-molded, and therefore pre-insert-molded and main insert-molded regions may partially overlap laterally.
In order to avoid a displacement of individual sections of the core elements of the lead frames with respect to one another and to ensure the desired position of the core elements, in the insert-molding die for the main insert-molding, necessary support regions are brought into contact with the pre-insert-molding such that the support regions ensure a positioning in the insert-molding die for the main insert-molding. However, this results in the main insert-molding not being able to completely surround the core element, but rather being interrupted at least at the support regions mentioned, and therefore partial regions of the pre-insert-molding are not covered and are outwardly exposed.
In the case of conventional lead frames, in particular if said lead frames have been used for forming controlling means, for example automatic transmission controlling means which are to be used in aggressive media, malfunctions have been observed.